1. Field of the Invention
This invention relates to new fluorocarbon siloxanes and to their use as curing agents in fluorocarbon silicone compositions.
2. Description of the Prior Art
New fluorocarbon silanes, siloxanes, and silicone compositions have been described by Kim, et al. in U.S. Pat. No. 3,542,830 and by Loree et al., in U.S. Pat. No. 3,647,740. The cured silicone compositions of Loree, et al. display increased resistance to the loss of elastomeric properties under confined conditions at elevated temperatures, a phenomenon known as reversion. In the extreme, this loss of elastomeric properties can result in the conversion of an elastomer to a soupy liquid. While the cured compositions of Loree, et al., have better reversion resistance than cured compositions based on poly(methyl-3,3,3-trifluoropropylsiloxane), the low temperature flexibility of the former do not equal that of the latter.
New fluorocarbon siloxanes and silicone compositions have been described by Yung K. Kim and Michael O. Riley in U.S. Application Ser. No. 572,583 of Apr. 28, 1975, entitled, "Low Temperature Reversion Resistant Organosilicon Polymers" now U.S. Pat. No. 3,975,362 and assigned to the assignee of this application which, in the cured state, display reversion resistance and improved low temperature flexibility.
The compositions of Loree, et al. and the compositions of Kim and Riley are curable with several curing agents including the crosslinking agents that are described by Holbrook in U.S. Pat. No. 3,344,160. However, in some instances, the reversion resistance of these new fluorocarbon siloxanes and silicone compositions is limited by the particular curing agent that is used to cure the composition. In particular, when certain compositions of Loree, et al., that contain silicon-bonded vinyl groups are cured with the crosslinking agents of Holbrook that contain silicon-bonded hydrogen atoms, reversion resistant is limited.